HG 9
2001
Spiders in Maryland
emerge from their white
web cells and find their way
outside.
There are many families of spiders, all of which are
predators. Spiders are not insects but belong to a closely
related group called arachnids. Some make webs; others
such as wolf spiders actively pursue their prey. Spiders
are common in trees, shrubs, herbaceous plants, and on
the ground in landscapes. Most spiders are generalized
predators, feeding on a wide range of prey (insects, other
spiders, etc.).
These spiders can bite humans
and cause a small irritating
spot which may not heal for 8
to 10 days.
Wolf Spiders
Most spiders are shy and harmless to humans. Normally,
they will not attempt to bite unless accidentally trapped or
held. They are beneficial by feeding on harmful insects.
Spiders are important in reducing the numbers of many
pest insects in gardens and landscape vegetation. Killing of
spiders should be avoided, if possible.
Wolf spiders are active
hunters and do not
construct webs. Some can
be fairly large and have
a frightening appearance.
They do not attack humans
even if they run across
one’s hand or foot, but if
handled or confined, they
can give a sharp bite. The
bite is not dangerous.
Spiders enter homes through screens, around windows,
doors and cracks. Maintaining tight fitting screens, weather
stripping and sealing cracks can help prevent spider entry
into the home. To discourage spider breeding near the home,
remove trash, piles of old lumber and bricks, weeds, leaves,
flower pots and any other objects piled or stacked next to the
house that provide areas where spiders can live undisturbed.
Wolf spiders come indoors most frequently in the fall and
are usually found in basements. Exclusion is the best way to
keep them outdoors.
Cobweb Spiders
Cobweb spiders are common household spiders that enter
homes when they are small. They build irregular webs in
areas where insects fly or rest, usually in corners of rooms or
windows. When they are active in the web, the web remains
relatively inconspicuous, but when these spiders leave a web
or die, the web becomes covered with dust and is easily seen.
Cleaning or dusting in areas frequented by these spiders is
sufficient for control.
Jumping Spiders
Jumping spiders move
in jumps or short, rapid
runs. They are frequently
found around windows
in search of prey such
as flies. They are often
black, quite hairy, and
as large as 1/3 inch long.
They may be marked
with red or white dots.
Jumping spiders generally
do not appear in large numbers and can be removed
individually.
Yellow House Spider
Yellow house spiders are small, about ¼ inch long, and
move rapidly. They may be found in all rooms of a house.
The spiders enter homes in early fall and are active for
several months weaving small white webs in confined spaces
where they spend the winter. In the spring, they usually
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Crab Spider
Crab spiders are bright white, yellow or reddish with their
legs projecting from their sides giving them the appearance
of a crab. They enter the home on cut flowers and cannot
survive indoors.
Black Widow Spider
The black widow is
common in Maryland,
but is not often found
indoors. These spiders
are most often found in
basement window wells,
beneath lawn benches or
porches, and in garages,
tool sheds, old lumber
piles, rock piles, trash piles, and water meters. Probably
they are most often brought inside in objects such as boxes,
flowerpots and baskets where they have established their
irregular webs.
The black widow female becomes mature in late summer and
fall. She is confined to her web and is very clumsy when
walking on a flat surface. Her appearance is as follows: body
about ½ inch long, jet black with a bright red hour glass
shape on the belly. This red mark is easily seen because she
hangs upside down in the web. Sometimes there may be
small dull red marks on the top of the abdomen and at the
tip. No other spider in Maryland looks like the black widow,
nor is any as poisonous. It is more dangerous to children
than adults.
The black widow is not aggressive. It will, however, bite
instinctively when touched or pressed, and for this reason
one should be very careful when working around areas where
black widows may be established. Take proper precautions:
wear gloves and pay attention to where you are working.
Black widow bites are sharp and painful. The victim should
go to the doctor immediately for treatment. It is important to
recognize this spider and describe the symptoms accurately
and fully so the physician can diagnose the trouble correctly.
To control the black widow, carefully remove all materials
where it might hide. This spider can be cleaned out of an
area simply by knocking the webs, spiders, and round,
tan egg sacs down with a stick and crushing them under
foot. Household insect sprays will kill the spiders when hit
directly.
Brown Recluse Spiders
The appearance of the
brown recluse spider
is unique. Its body is
about ¼ inch long, the
legs covering the area
of a coin the size of a
quarter. The front half
of the spider is marked
with a violin shaped
design and the rear half
of the abdomen is unmarked and tan or brown. All other
brown colored spiders this size have either no design at all or
have stripes or spot on the front half – never a violin shaped
design. Abdomens of other spiders are rarely unmarked but
generally exhibit spots, triangles or bands.
The brown recluse makes no conspicuous web, but moves
about rapidly. Bites are always contracted when the spider is
inadvertently pressed or touched.
This spider is not found in Maryland. It is a poisonous
spider principally found in the Midwest and Southwestern
United States. The bite of a brown recluse spider causes
a wound, which takes 6 weeks or more to heal. In rare
instances, it has caused death to sensitive individuals. This
spider, where it is common, is very shy and reclusive. It is
not active in rooms, which are commonly used, but stays in
storage areas, closets and infrequently used clothes and beds.
Adapated from: Wood, F.E., 1981. “Controlling Spiders in
Maryland”, Extension Bull. 241
Author: Mary Kay Malinoski, University of Maryland Extension Specialist, Home and
Garden Information Center
This publication is a series of publications of the University of Maryland Extension and The Home and Garden Information Center. For more information on related
publications and programs, http://extension.umd.edu/hgic. Please visit http://extension.umd.edu/ to find out more about Extension programs in Maryland.
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